There is a confusion regarding Pitru Paksha Shradh starting date
and time in 2013 as Hindu tithi starts early. Below are the detail beginning
time regarding Pitru Paksha in 2013.

Pitru Paksha Shradh Purnima Tithi Starts from 4:43 PM on
September 19 as per North Indian, Kannada and Telugu calendars. But Shradh is
not performed on the day as the day as per traditional Hindu calendars is
Chaturdasi Tithi.

Purnima Shradh is performed on September 19 before
4:43 PM.

Pitru Paksha Shradh Pratipada Tithi starts at 4:43 PM on September 19 as per North Indian calendars.

Pitru Paksha Pratipada Shradh is performed on the morning of September 20

In Marathi and Gujarati Calendars

Purnima Shradh is performed on September 19 morning.

Pitru Paksha Pratipada Shradh is performed on the morning of September 20

Please note common people do not observe Purnima Shradh and
they begin Shradh rituals with Pratipada Shradh.